Stabilization of aviation gasoline as detergent emulsion for lead determination by electrothermal atomic absorption spectrometry

The present work reports the development of a method for the determination of lead in aviation gasoline samples by electrothermal atomic absorption spectrometry (ETAAS). The samples were emulsified before injecting into the spectrometer in order to avoid the high instability observed in the signals when the samples were injected directly without any treatment. Stable detergent emulsions were obtained by mixing 1 mL of a 7% m/v Triton X-100 solution containing 10% v/v HNO3 with 4 mL of aviation gasoline. These emulsions generated constant integrated absorbance signals for 5 h at least. Several parameters related to the emulsion formation (Triton X-100 and HNO3 concentrations) and temperature program (pyrolysis and atomization temperatures and heating rate and the final temperature of the drying step) were evaluated. Both Triton X-100 and HNO3 concentrations in the solution used to form the emulsion influenced the sensitivity of the lead measurements as well as the heating rate utilized in the drying step. The use of a chemical modifier was necessary, being that the Pd conventional modifier presented better performance than the permanent Ir modifier. The limits of detection and quantification derived for the methodology were 1.2 and 4.0 μg L− 1. Six samples of aviation gasoline were analyzed and the lead concentrations varied between 11.6 and 64.2 μg L− 1. A recovery test was performed in order to attest the accuracy of the procedure and recovery percentages between 88 and 112% were observed.